Step 2: Make the parts

The parts can be cut or sawed out of one sheet of 4mm thick material, such as polycarbonate glass or wood. In this example I used 4mm birch plywood, which has been cut using a laser-cutter in a Fablab. The pdf with parts can be obtained from the page about the simpleWalker on my blog. For the polycarbonate version on the blog I have used a band saw instead of a laser cutter.

Step 3: Mount the RC servo's

The servo's can be mounted using 4 screws each. Using wood, self-tapping screws will suffice. Otherwise use nuts and bolts.

Step 4: Assemble the legs

Mount the servo-plates on the leg-plates using m2 screws. You might need to enlarge the drilled holes a little bit. The m2 screws don't need to take much force, they're mainly used as placeholders. The central m3 screw that bolts the leg to the servo shaft will take the load.

Don't tighten the central m3 screws yet. First you need to discover the servo's center-position in software. After centering the servo's (in arduino code with a servo range of [0-180] it means writing the value '80' to the servo) you can mount the legs at a straight angle.

I took the PDF and converted it to 3D printable STL files of the parts as well as a Mintronics "Menta" holder for the microcontroller. The prints are running right now. When this is done, do you mind if I post the STL files to Tinkercad linking back to this Instructable?

no problem, please make sure you credit me somewhere as original author :)

What I would really like to see is somebody skilled in scripting with OpenSCAD and do the conversion from 2d graphic to 3d model with one click - that would make the process much easier for making next models printable...

Hi Andy, I'm curious, why did you decide to add a microprocessor? You seem to describe your little guy here as a BEAM device, but it doesn't seem (to me, at least) very common to introduce a microprocessor at this level of complexity.

You are right. You could take out the electronics of the RC servo's and put in a BEAM bi-core. In 'the old days' of Tilden's beam robotics (when there were chunky 6502 or 68HC board around) a system with only two analog IC' s and a couple of capacitors was a great improvement. Now a microcontroller is just as easy (one atmel IC costing less than two dollar) and offers a great deal of flexibility in terms of adding sensors etc..

I believe steering is a function of timings with this morphology. Specifically (as far as i understand) the rear legs are normally (optimally?) a half phase (180 degrees or "anti phase") from the from legs - when the front leg is rotating in one direction the rear legs are rotating in the opposite direction. There are ways (given this configuration) to turn left and right, reverse, go forwards and "stomp" (where the robot is moving its legs but such motion doesn't cause it to move forwards) without any further physical alterations. Forward, stomp and reverse are a function of the phase. Steering is related to the amplitude of the signal sent for any given step forwards; a long left step and a short right results in a slight turn, over a number of steps this becomes an arc to the right. Hope this is useful, Drew p.s. "stomping" may appear useless but it can be very useful; for example your robot detects that moving its legs is harder than normal it could summarize that it has become stuck or bogged down. Imagine its traveling through a pile of leaves and is walking into and through the pile rather than over it, stomping could get it atop the otherwise untraversable pile of leaves.

Also, I'm currently experimenting with getting a beam robot walker to achieve static postures, so it would be able to posture for charging for example, or in order to get a better look around, would this be better as two Instructables (how to make the walker, how to get it to posture) or one with it all together? Thanks, Drew

On the contrary its a fairly standard BEAM layout, the real trick is in circuit design. There needs to be one or two modifications to more standard designs but these can easily be added on to an existing robot. I suppose a "built from scratch" approach would be more accessible and generally more clear, so I think i should still have one larger 'ible, as you advise. Thanks for your input, Drew